The operation of machines, particularly vehicles by persons under the influence of alcohol is a major safety problem in the United States and many other countries. Despite growing public awareness and government concern, statistics continue to show that a high percentage of automobile accidents causing serious injury or death involve drivers who have been drinking alcoholic beverages in excess. Injuries in the workplace are also often found to be related to the operation of heavy equipment or other machinery by persons impaired by the effects of alcohol.
Various attempts have been made to develop devices which prevent automobiles and the like from being operated by inebriated individuals. Such interlock devices typically operate according to the well known principle that the gas present in the alveoli of the lungs has an alcohol content directly proportional to that of the bloodstream. Blood alcohol content (B.A.C.) thus can be accurately determined by breath testing. A typical breath testing sobriety interlock of this general type is illustrated in U.S. Pat. No. 3,780,311 which shows an alcohol detection circuit connected to a vehicle ignition system to prevent the vehicle from starting if the driver's breath alcohol level exceeds a predetermined limit.
Although sobriety interlock systems are commercially available, they have not been embraced enthusiastically by the driving public as a whole. It is suspected that this reticence is based, at least in part, on a perception that sobriety interlock systems are inconvenient to use. In particular, it is suspected that many drivers believe that it would be unduly burdensome to be required to take and pass a breath sobriety test each and every time they need to start their car when they may only drink on occasion. Such drivers may be discouraged from installing a sobriety interlocking on their vehicle even though they may recognize the hazards of driving while intoxicated and would otherwise welcome the protection afforded by a sobriety interlock system which would prevent them from starting their vehicle if they were intoxicated.